doc/man7/provider-digest.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 provider-digest - The digest library E<lt>-E<gt> provider functions
   6
   7 =head1 SYNOPSIS
   8
   9 =for openssl multiple includes
  10
  11  #include <openssl/core_dispatch.h>
  12  #include <openssl/core_names.h>
  13
  14  /*
  15   * Digests support the following function signatures in OSSL_DISPATCH arrays.
  16   * (The function signatures are not actual functions).
  17   */
  18
  19  /* Context management */
  20  void *OSSL_FUNC_digest_newctx(void *provctx);
  21  void OSSL_FUNC_digest_freectx(void *dctx);
  22  void *OSSL_FUNC_digest_dupctx(void *dctx);
  23
  24  /* Digest generation */
  25  int OSSL_FUNC_digest_init(void *dctx);
  26  int OSSL_FUNC_digest_update(void *dctx, const unsigned char *in, size_t inl);
  27  int OSSL_FUNC_digest_final(void *dctx, unsigned char *out, size_t *outl,
  28                             size_t outsz);
  29  int OSSL_FUNC_digest_digest(void *provctx, const unsigned char *in, size_t inl,
  30                              unsigned char *out, size_t *outl, size_t outsz);
  31
  32  /* Digest parameter descriptors */
  33  const OSSL_PARAM *OSSL_FUNC_digest_gettable_params(void *provctx);
  34
  35  /* Digest operation parameter descriptors */
  36  const OSSL_PARAM *OSSL_FUNC_digest_gettable_ctx_params(void *dctx,
  37                                                         void *provctx);
  38  const OSSL_PARAM *OSSL_FUNC_digest_settable_ctx_params(void *dctx,
  39                                                         void *provctx);
  40
  41  /* Digest parameters */
  42  int OSSL_FUNC_digest_get_params(OSSL_PARAM params[]);
  43
  44  /* Digest operation parameters */
  45  int OSSL_FUNC_digest_set_ctx_params(void *dctx, const OSSL_PARAM params[]);
  46  int OSSL_FUNC_digest_get_ctx_params(void *dctx, OSSL_PARAM params[]);
  47
  48 =head1 DESCRIPTION
  49
  50 This documentation is primarily aimed at provider authors. See L<provider(7)>
  51 for further information.
  52
  53 The DIGEST operation enables providers to implement digest algorithms and make
  54 them available to applications via the API functions L<EVP_DigestInit_ex(3)>,
  55 L<EVP_DigestUpdate(3)> and L<EVP_DigestFinal(3)> (and other related functions).
  56
  57 All "functions" mentioned here are passed as function pointers between
  58 F<libcrypto> and the provider in B<OSSL_DISPATCH> arrays via
  59 B<OSSL_ALGORITHM> arrays that are returned by the provider's
  60 provider_query_operation() function
  61 (see L<provider-base(7)/Provider Functions>).
  62
  63 All these "functions" have a corresponding function type definition
  64 named B<OSSL_{name}_fn>, and a helper function to retrieve the
  65 function pointer from an B<OSSL_DISPATCH> element named
  66 B<OSSL_FUNC_{name}>.
  67 For example, the "function" OSSL_FUNC_digest_newctx() has these:
  68
  69  typedef void *(OSSL_OSSL_FUNC_digest_newctx_fn)(void *provctx);
  70  static ossl_inline OSSL_OSSL_FUNC_digest_newctx_fn
  71      OSSL_FUNC_digest_newctx(const OSSL_DISPATCH *opf);
  72
  73 B<OSSL_DISPATCH> arrays are indexed by numbers that are provided as
  74 macros in L<openssl-core_dispatch.h(7)>, as follows:
  75
  76  OSSL_FUNC_digest_newctx               OSSL_FUNC_DIGEST_NEWCTX
  77  OSSL_FUNC_digest_freectx              OSSL_FUNC_DIGEST_FREECTX
  78  OSSL_FUNC_digest_dupctx               OSSL_FUNC_DIGEST_DUPCTX
  79
  80  OSSL_FUNC_digest_init                 OSSL_FUNC_DIGEST_INIT
  81  OSSL_FUNC_digest_update               OSSL_FUNC_DIGEST_UPDATE
  82  OSSL_FUNC_digest_final                OSSL_FUNC_DIGEST_FINAL
  83  OSSL_FUNC_digest_digest               OSSL_FUNC_DIGEST_DIGEST
  84
  85  OSSL_FUNC_digest_get_params           OSSL_FUNC_DIGEST_GET_PARAMS
  86  OSSL_FUNC_digest_get_ctx_params       OSSL_FUNC_DIGEST_GET_CTX_PARAMS
  87  OSSL_FUNC_digest_set_ctx_params       OSSL_FUNC_DIGEST_SET_CTX_PARAMS
  88
  89  OSSL_FUNC_digest_gettable_params      OSSL_FUNC_DIGEST_GETTABLE_PARAMS
  90  OSSL_FUNC_digest_gettable_ctx_params  OSSL_FUNC_DIGEST_GETTABLE_CTX_PARAMS
  91  OSSL_FUNC_digest_settable_ctx_params  OSSL_FUNC_DIGEST_SETTABLE_CTX_PARAMS
  92
  93 A digest algorithm implementation may not implement all of these functions.
  94 In order to be usable all or none of OSSL_FUNC_digest_newctx, OSSL_FUNC_digest_freectx,
  95 OSSL_FUNC_digest_init, OSSL_FUNC_digest_update and OSSL_FUNC_digest_final should be implemented.
  96 All other functions are optional.
  97
  98 =head2 Context Management Functions
  99
 100 OSSL_FUNC_digest_newctx() should create and return a pointer to a provider side
 101 structure for holding context information during a digest operation.
 102 A pointer to this context will be passed back in a number of the other digest
 103 operation function calls.
 104 The parameter I<provctx> is the provider context generated during provider
 105 initialisation (see L<provider(7)>).
 106
 107 OSSL_FUNC_digest_freectx() is passed a pointer to the provider side digest context in
 108 the I<dctx> parameter.
 109 This function should free any resources associated with that context.
 110
 111 OSSL_FUNC_digest_dupctx() should duplicate the provider side digest context in the
 112 I<dctx> parameter and return the duplicate copy.
 113
 114 =head2 Digest Generation Functions
 115
 116 OSSL_FUNC_digest_init() initialises a digest operation given a newly created
 117 provider side digest context in the I<dctx> parameter.
 118
 119 OSSL_FUNC_digest_update() is called to supply data to be digested as part of a
 120 previously initialised digest operation.
 121 The I<dctx> parameter contains a pointer to a previously initialised provider
 122 side context.
 123 OSSL_FUNC_digest_update() should digest I<inl> bytes of data at the location pointed to
 124 by I<in>.
 125 OSSL_FUNC_digest_update() may be called multiple times for a single digest operation.
 126
 127 OSSL_FUNC_digest_final() generates a digest started through previous OSSL_FUNC_digest_init()
 128 and OSSL_FUNC_digest_update() calls.
 129 The I<dctx> parameter contains a pointer to the provider side context.
 130 The digest should be written to I<*out> and the length of the digest to
 131 I<*outl>.
 132 The digest should not exceed I<outsz> bytes.
 133
 134 OSSL_FUNC_digest_digest() is a "oneshot" digest function.
 135 No provider side digest context is used.
 136 Instead the provider context that was created during provider initialisation is
 137 passed in the I<provctx> parameter (see L<provider(7)>).
 138 I<inl> bytes at I<in> should be digested and the result should be stored at
 139 I<out>. The length of the digest should be stored in I<*outl> which should not
 140 exceed I<outsz> bytes.
 141
 142 =head2 Digest Parameters
 143
 144 See L<OSSL_PARAM(3)> for further details on the parameters structure used by
 145 these functions.
 146
 147 OSSL_FUNC_digest_get_params() gets details of the algorithm implementation
 148 and stores them in I<params>.
 149
 150 OSSL_FUNC_digest_set_ctx_params() sets digest operation parameters for the
 151 provider side digest context I<dctx> to I<params>.
 152 Any parameter settings are additional to any that were previously set.
 153
 154 OSSL_FUNC_digest_get_ctx_params() gets digest operation details details from
 155 the given provider side digest context I<dctx> and stores them in I<params>.
 156
 157 OSSL_FUNC_digest_gettable_params() returns a constant B<OSSL_PARAM> array
 158 containing descriptors of the parameters that OSSL_FUNC_digest_get_params()
 159 can handle.
 160
 161 OSSL_FUNC_digest_gettable_ctx_params() and
 162 OSSL_FUNC_digest_settable_ctx_params() both return constant
 163 B<OSSL_PARAM> arrays as descriptors of the parameters that
 164 OSSL_FUNC_digest_get_ctx_params() and OSSL_FUNC_digest_set_ctx_params()
 165 can handle, respectively.  The array is based on the current state of
 166 the provider side context if I<dctx> is not NULL and on the provider
 167 side algorithm I<provctx> otherwise.
 168
 169 Parameters currently recognised by built-in digests with this function
 170 are as follows. Not all parameters are relevant to, or are understood
 171 by all digests:
 172
 173 =over 4
 174
 175 =item "blocksize" (B<OSSL_DIGEST_PARAM_BLOCK_SIZE>) <unsigned integer>
 176
 177 The digest block size.
 178 The length of the "blocksize" parameter should not exceed that of a B<size_t>.
 179
 180 =item "size" (B<OSSL_DIGEST_PARAM_SIZE>) <unsigned integer>
 181
 182 The digest output size.
 183 The length of the "size" parameter should not exceed that of a B<size_t>.
 184
 185 =item "flags" (B<OSSL_DIGEST_PARAM_FLAGS>) <unsigned integer>
 186
 187 Diverse flags that describe exceptional behaviour for the digest:
 188
 189 =over 4
 190
 191 =item B<EVP_MD_FLAG_ONESHOT>
 192
 193 This digest method can only handle one block of input.
 194
 195 =item B<EVP_MD_FLAG_XOF>
 196
 197 This digest method is an extensible-output function (XOF) and supports
 198 setting the B<OSSL_DIGEST_PARAM_XOFLEN> parameter.
 199
 200 =item B<EVP_MD_FLAG_DIGALGID_NULL>
 201
 202 When setting up a DigestAlgorithmIdentifier, this flag will have the
 203 parameter set to NULL by default.  Use this for PKCS#1.  I<Note: if
 204 combined with EVP_MD_FLAG_DIGALGID_ABSENT, the latter will override.>
 205
 206 =item B<EVP_MD_FLAG_DIGALGID_ABSENT>
 207
 208 When setting up a DigestAlgorithmIdentifier, this flag will have the
 209 parameter be left absent by default.  I<Note: if combined with
 210 EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
 211
 212 =item B<EVP_MD_FLAG_DIGALGID_CUSTOM>
 213
 214 Custom DigestAlgorithmIdentifier handling via ctrl, with
 215 B<EVP_MD_FLAG_DIGALGID_ABSENT> as default.  I<Note: if combined with
 216 EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
 217 Currently unused.
 218
 219 =back
 220
 221 The length of the "flags" parameter should equal that of an
 222 B<unsigned long int>.
 223
 224 =back
 225
 226 =head2 Digest Context Parameters
 227
 228 OSSL_FUNC_digest_set_ctx_params() sets digest parameters associated with the
 229 given provider side digest context I<dctx> to I<params>.
 230 Any parameter settings are additional to any that were previously set.
 231 See L<OSSL_PARAM(3)> for further details on the parameters structure.
 232
 233 OSSL_FUNC_digest_get_ctx_params() gets details of currently set parameters
 234 values associated with the give provider side digest context I<dctx>
 235 and stores them in I<params>.
 236 See L<OSSL_PARAM(3)> for further details on the parameters structure.
 237
 238 =head1 RETURN VALUES
 239
 240 OSSL_FUNC_digest_newctx() and OSSL_FUNC_digest_dupctx() should return the newly created
 241 provider side digest context, or NULL on failure.
 242
 243 OSSL_FUNC_digest_init(), OSSL_FUNC_digest_update(), OSSL_FUNC_digest_final(), OSSL_FUNC_digest_digest(),
 244 OSSL_FUNC_digest_set_params() and OSSL_FUNC_digest_get_params() should return 1 for success or
 245 0 on error.
 246
 247 OSSL_FUNC_digest_size() should return the digest size.
 248
 249 OSSL_FUNC_digest_block_size() should return the block size of the underlying digest
 250 algorithm.
 251
 252 =head1 BUGS
 253
 254 The EVP_Digest() and EVP_DigestFinal_ex() libcrypto API calls do not
 255 expect the digest size to be larger than EVP_MAX_MD_SIZE. Any algorithm which
 256 produces larger digests is unusable with those API calls.
 257
 258 =head1 SEE ALSO
 259
 260 L<provider(7)>, L<OSSL_PROVIDER-FIPS(7)>, L<OSSL_PROVIDER-default(7)>,
 261 L<OSSL_PROVIDER-legacy(7)>
 262
 263 =head1 HISTORY
 264
 265 The provider DIGEST interface was introduced in OpenSSL 3.0.
 266
 267 =head1 COPYRIGHT
 268
 269 Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
 270
 271 Licensed under the Apache License 2.0 (the "License").  You may not use
 272 this file except in compliance with the License.  You can obtain a copy
 273 in the file LICENSE in the source distribution or at
 274 L<https://www.openssl.org/source/license.html>.
 275
 276 =cut